1. Field of the Invention
The present invention relates to a coil portion insulating construction for a dynamoelectric machine such as an automotive alternator, etc., and particularly relates to an insulating construction for a stator coil, or a field coil, etc.
2. Description of the Related Art
In conventional automotive alternators, coil portions that are formed by winding enameled wire onto a stator core, or a rotor core, etc., have been impregnated with insulating resins such as unsaturated polyester resins, or polyester resins to which epoxy resins have been added, etc., to increase insulation of the coil portions.
Coil portion insulating constructions in which enameled wires that have enamel coatings that have polyamideimide resin layers were used and epoxy-modified polyesterimide resins were used as insulating resins have been disclosed, such as in Patent Literature 1, for example.
[Patent Literature 1]
Japanese Patent Laid-Open No. 2005-328584 (Gazette)
Since automotive alternators of this kind are exposed to high temperatures and vibrations for long periods, not only initial adhesive strength is required of the insulating resin of the coil portion insulating construction, but also adhesive strength that is high for long periods. For insulating resins that are applied to and impregnated into coil portions that are formed by winding enameled wires onto stator cores, or rotor cores, etc., in particular, not only high adhesive strength is required but also increased insulation. Thus, one problem has been that the service life of enamel coatings may be affected if compatibility between the enamel coatings and the insulating resins is poor, giving rise to early insulation failure.
Because automotive alternators are mass-produced, high productivity is also required. Because the enameled wires are bent and deformed in the process of winding the enameled wires, large mechanical loads act on the enameled wires, imparting damage to the enamel coatings. It is necessary to select the insulating resins that are applied and impregnated in subsequent steps so as not to have adverse effects that might damage the enamel coatings.
Since the epoxy-modified polyesterimide resin that is disclosed in Patent Literature 1 has extremely rigid properties, large shearing stresses may arise between the insulating resin and the enamel coatings if the epoxy-modified polyesterimide resin is used as the insulating resin, imparting damage to the enamel coatings and reducing the service life of the enamel coatings.